1. Field of the Invention
The present invention relates to an apparatus for producing two-dimensionally bent and optionally tempered glass plates, with a roller oven for heating planar glass plates in a horizontal position to the bending temperature, a pressing and bending unit following the roller oven and a cooling device following the pressing and bending unit.
2. Background of the Related Art
In a known apparatus for producing cylindrically bent glass plates, the conveying rollers have in the end portion of the roller oven a curvature which increases from roller to roller. The glass plate to be bent is conveyed into the bending station on the conveying rollers. The pressing and bending unit comprises a full or solid surface bending mold positioned above the conveying rollers and a frame bending mold lowerable below the supporting regions of the conveying rollers with which the glass plate is pressed against the upper full surface bending mold. The pressing process is followed by the bent glass plate again being placed on the conveying rollers with the aid of which it is brought into the following cooling station (German Patent 34 38 705).
In order to reduce the deterioration to the optical quality of the heated glass plates resting on the conveying rollers within the bending station under the effect of the weight of the plates, in the known apparatus part of the glass plate weight is compensated by a hot gas flow directed from below against the glass plate between the conveying rollers. Despite these measures it is not possible to completely eliminate the influence of the non-uniform supporting of the glass plate by the conveying rollers. In addition, the known apparatus is relatively complicated and costly.